Conventionally, as a refrigerator having a freezing cycle of sending a refrigerant to two evaporators using a two-stage compressor, the following is proposed.
Namely, a refrigerator with an on-off valve installed at an exit of a condenser is proposed, which by switching the on-off valve, executes a simultaneous cooling mode for supplying a refrigerant sequentially to a refrigerating evaporator (hereinafter referred to as an R evaporator) and a freezing evaporator (hereinafter referred to as an F evaporator), and thereby for simultaneously cooling the R evaporator and the F evaporator, or executes a cooling mode for supplying a refrigerant only to a freezing evaporator (hereinafter referred to as an F evaporator) via a bypass tube from the on-off valve (for example, refer to Patent Document 1).
[Patent Document 1] Japanese Patent Disclosure (Kokai) 2002-31459
In the refrigerator aforementioned, in the simultaneous cooling mode for simultaneously cooling the refrigerating chamber and freezing chamber, the evaporation temperature of the R evaporator and the evaporation temperature of the F evaporator are the same, thus a problem arises that the efficiency of the freezing cycle cannot be improved.
Further, the absolute value of the evaporation temperature of the R evaporator is low, so that a problem arises that the relative humidity in the refrigerating chamber is low.
Furthermore, the on-off valve is switched when it is necessary to cool each of the freezing chamber and the refrigerating chamber, so that a loss is caused in the on-off valve and the temperature of either of the chambers rises during the waiting time in the alternate cooling, and thus a problem arises that the temperature cannot be set finely and a higher constant temperature performance cannot be obtained.
A refrigerator in wide use as a domestic article generally has a section of a freezing temperature zone and a section of a refrigerating temperature zone, and in a refrigerator of a type of cooling inside the refrigerator by one evaporator, a distribution of cooled air to the freezing section and the refrigerating section is controlled by a damper, and according to the overall load, a compressor is controlled for on and off. Further, in a type of controlling a number of revolutions of the compressor by an inverter, the number of the revolutions is further controlled finely. In the refrigerator having such a constitution, a refrigerant is evaporated so as to make the exit temperature of the evaporator equal to the temperature of the cooling section.
Furthermore, in recent years, as a type having a freezing evaporator and a refrigerating evaporator respectively in a freezing section and a refrigerating section, there is a refrigerator in which the refrigerating evaporator and the freezing evaporator are connected in series. This refrigerator can simultaneously cool the two sections of the freezing section and the refrigerating section, though a suction pressure of the compressor is restricted by a pressure of the freezing evaporator having a low evaporation temperature, so that it is difficult to enhance the efficiency of the freezing cycle.
On the other hand, in a refrigerator in which a freezing evaporator and a refrigerating evaporator are connected in parallel and are cooled alternately, a check valve is added and it is controlled so as to increase the evaporation temperature of the refrigerating evaporator for cooling the refrigerating chamber, thus the efficiency of the freezing cycle can be enhanced, though the sections of the two temperature zones cannot be cooled simultaneously.
[Patent Document 2] Japanese Patent Disclosure (Kokai) 2001-12634
[Patent Document 3] Japanese Patent Disclosure (Kokai) 2002-147896
[Patent Document 4] Japanese Patent Disclosure (Kokai) 2001-278934
In the constitution that a freezing evaporator and a refrigerating evaporator are connected in parallel, a refrigerator is considered, which is provided with a refrigerant flow rate adjustment device for distributing a refrigerant supplied to the two evaporators from the condenser and for adjusting the refrigerant flow rate, and simultaneously supplies the refrigerant to the freezing evaporator and refrigerating evaporator and simultaneously cools the sections of the two temperature zones.
In such a constitution, the refrigerant is distributed to the freezing evaporator and refrigerating evaporator by the flow rate resistance of capillary tubes connecting the condenser and evaporators, and it is difficult to control the refrigerant flow rate flowing through the capillary tubes depending on the condition of each evaporator, so that the cooling capacity of each evaporator cannot be controlled.
Therefore, the applicant considers developing an adjustment valve for adjusting the refrigerant flow ratio (rate to the maximum flow) to the freezing evaporator and the refrigerating evaporator according to the opening of the valve body and to limit and adjust the refrigerant flow rate to one evaporator according to the opening of the valve body. Namely, for example, it is to limit and adjust the refrigerant flow rate to the refrigerating evaporator (the refrigerant flow rate to the freezing evaporator is maximum), thereby to realize a simultaneous supply of the refrigerant to the freezing evaporator and refrigerating evaporator.
However, an appropriate refrigerant amount to the evaporators is always varied according to the operating condition of the refrigerator, so that even if the refrigerant flow rate to one evaporator is limited and adjusted, there is no method available for correctly judging whether the refrigerant flow rate to one evaporator is appropriate or not, and a problem is left unsolved that the flow rate adjustment cannot be executed appropriately.
Therefore, it is considered to install temperature sensors for detecting an entrance temperature and an exit temperature of one evaporator, to obtain a superheat amount (the difference between the exit temperature and the entrance temperature) of one evaporator from the temperature sensors, and to control appropriately the superheat amount, though when the accuracy of the temperature sensors is low, the control on the basis of such a superheat amount is difficult.
Further, as a result of limiting and adjusting the refrigerant flow rate to one evaporator, when the supply of the refrigerant to one evaporator is stopped or the refrigerant flow rate is limited to a minimum refrigerant flow ratio, even if the refrigerant is next supplied to one evaporator, a delay is caused under the ordinary control until a sufficient refrigerant is supplied to one evaporator, and there is a fear that obstacles may be caused in limiting and adjusting one evaporator.
The present invention, with the foregoing problems in view, provides a refrigerator having a two-stage compressor for efficiently cooling both a refrigerating chamber and a freezing chamber.
Further, the present invention was developed with the foregoing in view, and is intended to provide a refrigerator of a type of supplying a refrigerant to an evaporator for a freezing chamber and an evaporator for a refrigerating chamber, wherein when, on the basis of a superheat amount which is a difference between an exit temperature of one evaporator and an entrance temperature thereof, limiting and adjusting a refrigerant flow rate to one evaporator according to an opening of a valve body so as to make the superheat amount of one evaporator appropriate, the entrance temperature of one evaporator and the exit temperature thereof can be detected accurately.
Furthermore, the present invention was developed with the foregoing in view, and is intended to provide a refrigerator of a type of supplying a refrigerant to an evaporator for a freezing chamber and an evaporator for a refrigerating chamber, wherein when limiting and adjusting a refrigerant flow rate to one evaporator according to an opening of a valve body, no delay is caused to refrigerant supply to one evaporator.